topic Re: Change symbology of an existing layer through arcpy in ArcGIS Pro Questions

Change symbology of an existing layer through arcpy

TorbjørnDalløkken2 — Thu, 30 Mar 2023 15:09:26 GMT

Hi.

I've created a pythonscript contained in an ArcGIS Pro Toolbox (atbx), where I'd like to change a layer's symbology. I know it's possible to define a layer's symbology through the script parameters in the toolbox by setting the output layer as derived and also defining a lyrx file either as a property ofthe parameter or in the script it self. But in my case, the layer that I want to change symbology for is already added in the ArcGIS Pro project and is being used in a task. Therefore it's not possible for me to remove and add the layer as a derived parameter, since the task-resource for that layer will be broken.

I've tried using arcpy.ApplySymbologyFromLayer, but that doesn't work. There are no errors, but the layer symbology does not change. The lyrx-file works when importing symbology manually in Pro. What's the best practice here? Does anyone know what might be causing ApplySymbologyFromLayer to not have any effect?

One option is to define the new symbology based on the CIM-class, for example CIMUniqueValueRenderer. I've almost created the symbology this way, but I'm not able to set the defaultLabel. The symbology should show only to groups, <Null> and "All other Values". Has anyone got any experience with this?

Re: Change symbology of an existing layer through arcpy

DavidPike — Thu, 30 Mar 2023 16:17:20 GMT

Seems to be a common issue. MXDs did have a refreshActiveView which I cant see for Pro.
This hack might be worth a go:

https://gis.stackexchange.com/questions/283750/why-would-arcpy-applysymbologyfromlayer-tool-not-work-in-arcgis-pro-python-windo

"I found that passing a layer object through the ApplySymbologyFromLayer() function, as the first arg, does not work. For whatever reason, you should pass a string through it. So basically change your line from:"

in_layer = arcpy.ApplySymbologyFromLayer_management(in_layer,in_symbology_layer,update_symbology="MAINTAIN")[0]

to:

in_layer = arcpy.ApplySymbologyFromLayer_management(str(in_layer),in_symbology_layer,update_symbology="MAINTAIN")[0]

Re: Change symbology of an existing layer through arcpy

TorbjørnDalløkken2 — Fri, 31 Mar 2023 07:56:13 GMT

I just tried using string instead of layer in the ApplySymbologyFromLayer() function, and the results are the same. No errors returned, and the layer symbology does not change..

Re: Change symbology of an existing layer through arcpy

JeffBarrette — Thu, 06 Apr 2023 02:42:10 GMT

Hello @TorbjørnDalløkken2 .

Have you taken a look at the arcpy.mp module. We support a limited number of renderers currently but UniqueValue is one of them.

Here are a couple of starting points

https://pro.arcgis.com/en/pro-app/latest/arcpy/mapping/symbology-class.htm

https://pro.arcgis.com/en/pro-app/latest/arcpy/mapping/uniquevaluerenderer-class.htm

And then Python CIM Access could be used to modify properties not exposed to the API.

https://pro.arcgis.com/en/pro-app/latest/arcpy/mapping/python-cim-access.htm

Jeff - Layout and arcpy.mp teams

Re: Change symbology of an existing layer through arcpy

SGTomlins — Fri, 13 Oct 2023 18:13:05 GMT

This code worked for me..

p2 = arcpy.mp.ArcGISProject(aprfilenew)
maps = p2.listMaps()
for map in maps:
    print ('--------------------------------------------------------------')
    print (map.name)
    print ('--------------------------------------------------------------')
    layers = map.listLayers()
    for layer in layers:
        if layer.supports('NAME') and layer.supports('LONGNAME') \
                    and layer.supports('DATASOURCE'):
            print (layer.longName + ' ---> ' + layer.dataSource)
        print(layer.longName)

        newfeaturelayer = layer.longName
        arcpy.MakeFeatureLayer_management(layer, newfeaturelayer)
        newLayerout = newfeaturelayer + "-az"  # ## rename this as needed....

        arcpy.ApplySymbologyFromLayer_management(newfeaturelayer, layer)

        arcpy.SaveToLayerFile_management(newfeaturelayer, path + newLayerout + '.lyrx', "ABSOLUTE")

Re: Change symbology of an existing layer through arcpy

JohnGaiot — Fri, 22 Mar 2024 20:59:00 GMT

Why do we have to perform all this coding when simply importing a saved layer file (lyr or lyrx) should work programmatically? In other words, what's the point of having the "Apply Symbology From Layer" function when it's not doing what it's supposed to be doing?

Re: Change symbology of an existing layer through arcpy

Jeff_Lee — Wed, 16 Apr 2025 21:27:46 GMT

Still hasn't been fixed. I have 300 layers for which I have to apply a predefined symbology and I'm having the same problems.

Re: Change symbology of an existing layer through arcpy

KellyJanus1 — Wed, 17 Dec 2025 14:57:35 GMT

I'm having the same issue. I have a symbology that I need to apply to 100 maps. After making one map manually with the desired symbology, I exported the symbology to a .lyrx file. I wrote a python script to walk through my folder containing all 99 of my maps and I applied the python tool "arcpy.management.ApplySymbologyFromLayer()" to apply my .lyrx file to every appropriate layer.

I ran the code with no errors and when I went back to open my maps, none of the symbology changed.

While there may be a new trick or modification to fix this problem, my code "should" work because the python code I am applying matches the python code used in the ArcPro guidelines. Also, thank you to everyone providing alternative code in the comments. Trying that now.